People told to stay clear of the tiny capsule containing Caesium-137, which emits radiation equal to 10 X-rays per hour.
The loss of the radioactive capsule, which is believed to have fallen from a truck that travelled some 1,400km (870 miles) across Western Australia, has triggered a weeklong search and a radiation alert for large parts of the state.
On Tuesday, the Australian Radiation Protection and Nuclear Safety Agency said it was working with the Western Australian government to locate the capsule. The Australian Nuclear Science and Technology Organisation also sent radiation services specialists as well as detection and imaging equipment.
The capsule, part of a gauge used to measure the density of iron ore, had been entrusted by Rio Tinto Ltd to a specialist contractor to transport. Rio apologised on Monday for the loss, which happened sometime in the past two weeks. The truck had travelled from north of Newman, a small town in the remote Kimberley region, to a storage facility in the northeast suburbs of Perth – a distance longer than the length of Britain.
Western Australia Chief Health Officer Andrew Robertson said under strict regulations radioactive material is regularly transported around Western Australia.
“It is extremely rare for a source to be lost,” he said in a statement.
State emergency officials on Tuesday issued a new alert to motorists along Australia’s longest highway to take care when approaching the capsule search parties, as vehicles carrying the radiation detectors are travelling at slow speeds along the highway
“It will take approximately five days to travel the original route, an estimated 1400kms, with crews travelling north and south along Great Northern Highway,” Department of Fire and Emergency Services (DFES) incident controller, Darryl Ray, said in a statement late on Monday.
The capsule was picked up from Rio Tinto’s Gudai-Darri mine site on January 12. When it was unpacked for inspection on January 25, the gauge was found broken apart, with one of four mounting bolts missing and screws from the gauge also gone.
Authorities suspect vibrations from the truck caused the screws and the bolt to come loose, and the capsule fell out of the package and then out of a gap in the truck.
The silver capsule, just 6mm (0.24 inches) wide and 8mm (0.31 inches) long, contains Caesium-137 which emits radiation equal to 10 X-rays per hour. People have been told to stay at least 5 metres (16.5 feet) away as exposure could cause radiation burns or radiation sickness, though experts have said driving past the capsule would be relatively low risk, akin to taking an X-ray.
The capsule does not pose a danger to passers-by who do not linger, said Edward Obbard, senior lecturer in Nuclear Engineering at the University of New South Wales, Sydney.
“If you were standing a metre away from it for an hour, you would receive a radiation dose of around 1 millisievert. That’s about one-twentieth of the dose people who work with radiation are allowed to get in a year,” Obbard wrote in The Conversation.
“If you were much closer to the capsule, say 10cm or so, you’d be getting around 100 millisievert per hour, which could do you some real damage,” he said.
If the capsule remains missing, it will pose a danger for “the next century or so”, according to Obbard. The concern is that such a threat may be forgotten with the passage of time.
“Will anyone remember?” Obbard asked
“If you came across a tiny cylinder on the road today, you’d know to keep your distance – but what about if you found it in five years, or in 20 years?”
